It has long been desirable in the manufacture of tissue paper to increase bulk. Increased bulk provides economic advantages, product performance advantages, and customer preference advantages to the tissue product.
The bulk of a paper sheet is inversely related to the density of the sheet. As the density of the sheet decreases, i.e., density values become smaller, the bulk of the sheet would increase. The density of a paper sheet may be measured as grams per centimeter cube (g/cm3) or similar weight over volume measurement. Bulk measurements for tissues are typically reported as cm3/g.
It has long been known in the paper making arts that increased bulk can be obtained by adhering a wet web of paper fibers to the surface of a Yankee dryer, or other similar smooth drying surface, drying the web to form a paper sheet and then creping the paper sheet from the dryer surface. Creping, however, can result in certain undesirable side effects. In particular, creping increases the roughness of the sheet by creating a surface contour having a series of ridges and troughs (hills and valleys) running across the width (cross-machine direction) of the sheet. Thus, a creped sheet may feel rough, if not very rough, to a user of the tissue.
The present invention provides a new and useful way in which to obtain the increased bulk of a creped tissue, while avoiding the surface roughness associated with creping.
In an embodiment of this invention, there is provided a tissue made by creping a sheet of paper making fibers from a Yankee dryer; the sheet further comprising: a first side and a second side; the first side being in contact with the surface of the Yankee dryer; the second side being positioned away from the surface of the Yankee dryer; the first side of the sheet having a surface, said surface having a uniformly smooth appearance; a bulk of at least (i.e., greater than or equal to) about 6 cm3/g at least about 7 cm3/g, or at least about 8 cm3/g; and, a stretch of at least about 10% in the machine direction. This tissue may have the second side of the sheet comprising a creped pattern. This tissue may also be a blended single layer sheet.
In another embodiment of this invention there is provided a multi-ply tissue product having a smooth outer surface comprising: a first base sheet made by creping a sheet of material from a Yankee dryer; the base sheet further comprising: a first side and a second side; the first side being in contact with the surface of the Yankee dryer; the second side being positioned away from the surface of the Yankee dryer; the first side of the base sheet having a smooth surface substantially free from any creped pattern; and, the second side of the base sheet having a creped pattern, a second base sheet; the first and second base sheets being positioned together to form a multi-ply product; and, the first side of the first base sheet constituting the smooth outer surface of the multi-ply tissue. This multi-ply tissue may have the second base sheet further made by creping the base sheet from a Yankee dryer; the base sheet further comprising: a first side and a second side; the first side being in contact with the surface of the Yankee dryer; the second side being positioned away from the surface of the Yankee dryer; the first side of the base sheet having a smooth surface; and, the second side of the base sheet having a creped pattern.
In yet a further embodiment there is provided single layer base tissue sheet having a basis weight from about 10 to 25 gsm, a bulk of from about 6 cm3/g to about 15 cm3/g, and a stretch of from about 10% to about 50% in the machine direction; and comprising a Yankee side and an off-Yankee side; the Yankee side having a smooth surface, substantially free from any discernable crepe pattern.
In yet another embodiment there is provided a multilayer tissue made by creping the tissue from a dryer and further comprising: a top and a bottom layer; the bottom layer comprising: a first side; the first side being in contact with the surface of the Yankee dryer; the first side having a uniformly smooth surface; the top layer comprising; a second side; the second side being positioned away from the surface of the Yankee dryer; the second side having a creped pattern.